1. Field of the Invention
The present invention generally relates to remote optical sensing and more specifically, to a mutually pumped phase conjugator remote optical sensing technique and system utilized as a real time communications link for Identification of Friend or Foe (IFF).
2. Description of Prior Art
The diverse deployment of highly sophisticated weapon systems by numerous participants on the modern battlefield can pose a problem not only to battlefield tactics but also to friendly forces in battlefield engagements. Digital signals permit the integration of speech, data, pictures, or any other information in a universal communications format. A real-time communication link which cannot be easily countermeasured is crucial to battlefield success. This fact has led to a greater dependence on updated information only available through digital information transmission.
A communications link is especially crucial in preventing accidental engagement of friendly forces on the battlefield which creates tremendous morale problems and reduces the overall effectiveness of any engagement. In the area of IFF it is essential to positively identify friendly forces quickly and accurately with absolute assurance in order to effectively engage unfriendly forces. The uncertainty in the identification of forces on the battlefield and subsequent hesitation in engagements can lead to an ineffective encounter (fratricide in the worst case). Some of the problems, past solutions and their defects in IFF can be described in the context of engagements that occurred during Desert Storm.
In Desert Storm, ranges of 2-4 km for tank engagements and as much as 8 km for some guided munitions reduced the target seen by the soldier to a "blob". The desert terrain presents an uncluttered extended view, with few visual spatial cues, and no natural places of concealment. Flags, inverted Vee and other identifying symbols fabricated using paint/tape, and orange panels were placed on vehicles to aid in daylight visual recognition. Heavy overcast days, smoke, and nighttime encounters led to the aforementioned solutions as being unusable, and also could easily be countermeasured since special equipment was not required to determine the presence of such measures. Numerous nighttime engagements required use of infrared imaging devices which also suffered from problems due to the surroundings.
Thermal terrain images in the Dessert differ from more temperate terrains because of low thermal scene contrast and large target contrast swings due to diurnal cycles which make thermal imaging difficult. Temperature cycles as large as 70 degree F. occur from day to night. When gain/contrast controls of thermal imaging devices are set to maximize brightness, recognition cues are severely reduced. Temporary solutions, such as pulsing near IR beacons were utilized on vehicles but was not appropriate for a longer conflict since the enemy also had limited night vision devices. These types of solutions have a fixed recognition which cannot be readily updated, and allow for a less complicated countermeasure to be designed since each party requires only a transmitter or a receiver.
While the prior art has reported using IFF systems and techniques none have established a basis for a specific apparatus that is dedicated to the task of resolving the particular problem at hand. What is needed in this instance is a universal IFF apparatus and technique which includes: wavelengths utilized not in the visible spectrum, recognition requirements that can be continually updated, requires transmitting and receiving devices for both parties (universal) which must be nominally of the same wavelength allows for the immediate transferral of digital information between both parties, and not substantially dependent on environmental conditions.